fix: switch explain to Groq free tier

pipeline/explainer.py

@@ -29,17 +29,18 @@ class FallacyExplainer:
     DEFAULT_FALLACY_CLASSES = list(FALLACY_DEFINITIONS.keys())
 
     def __init__(self, fallacy_classes=None, fallacy_definitions=None):
-        model_id = os.environ.get("EXPLAIN_MODEL_ID", DEFAULT_MODEL_ID)
+        self._model_id = os.environ.get("EXPLAIN_MODEL_ID", DEFAULT_MODEL_ID)
         self._client = InferenceClient(
-            model=model_id,
-            token=os.environ["HUGGINGFACE_TOKEN"],
+            provider="groq",
+            api_key=os.environ["GROQ_API_KEY"],
         )
         self.fallacy_classes = fallacy_classes or self.DEFAULT_FALLACY_CLASSES
         self.fallacy_definitions = fallacy_definitions or FALLACY_DEFINITIONS
-        print(f"FallacyExplainer ready (model: {model_id})")
+        print(f"FallacyExplainer ready (model: {self._model_id} via Groq)")
 
     def _generate_with_prompt(self, prompt_text, max_new_tokens=128):
         result = self._client.chat_completion(
+            model=self._model_id,
             messages=[{"role": "user", "content": prompt_text}],
             max_tokens=max_new_tokens,
             temperature=0.1,